The present invention relates to an air conditioner used to control the internal temperature, humidity, oxygen partial pressure and pressure of aircraft, including fixed-wing aircraft and rotating-wing aircraft.
As air conditioners in aircraft, conventionally air cycle cooling devices were chiefly employed in which temperature-adjusted and pressure-adjusted cooled air is obtained by using a radial compressor to perform adiabatic compression of extracted air compressed in a compression section of an engine, after subjecting the air to heat exchanging with external air for cooling, and by using an expansion turbine to perform adiabatic expansion of the air after again subjecting the adiabatic compressed air to heat exchanging with external air for cooling.
Specifically, in the conventional aircraft air conditioner shown in FIG. 16, air extracted from engine 101 is cooled by a heat exchanger called a pre-cooler 102 before being practically adiabatically compressed by a radial compressor 103; the air which has thereby been raised in temperature is cooled by a heat exchanger called a main cooler 104 and practically adiabatically expanded by expansion turbine 105. Cooled air is thereby obtained. In this pre-cooler 102 and main cooler 104, cooling is performed by external air passing through ram air flow path 109. The expansion work of this expansion turbine 105 is utilized as compressive power by being transmitted to compressor 103 through shaft 106. It should be noted that when the aircraft is on the ground or in low-level flight, the external air temperature is high and the moisture content of the air is high, so when expansion takes place in the expansion turbine 105, moisture in the air condenses and a mist of water droplets is formed. A water separator 107 is therefore arranged downstream of expansion turbine 105 to capture the moisture. Cabin cooling is performed by supplying the cooled air that has passed through this water separator 107 to the interior of cabin 108, including the cockpit space of the aircraft. If the engine is stopped while the aircraft is on the ground, it is arranged to be possible to supply extracted air from a high-pressure air supply unit such as an auxiliary engine called an auxiliary power unit, instead of engine 101, to the air conditioner.
In order to perform cabin heating at high altitude etc., a bypass air flow path 111 is provided to feed air extracted from engine 101 into cabin 108; this bypass air flow path 111 is opened/closed by means of a hot-air modulating valve 112. Some of the extracted air is fed to a mixing duct 113 arranged downstream of water separator 107 instead of being cooled by the air cycle cooling device constituted by compressor 103 and expansion turbine 105, by opening this hot-air modulating valve 112. In this mixing duct 113, extracted air cooled by the air cycle cooling device and extracted air that has not been cooled are mixed. Air of a suitable temperature is thus obtained by adjusting the degree of opening of hot-air modulating valve 112. Cabin heating can be performed by supplying this air of suitable temperature into cabin 108. When cruising at high altitude, the ram air flow path 109 is throttled, so the air extracted from engine 101 is kept in a moderately high temperature since it is not excessively cooled in pre-cooler 102 or main cooler 104. The air within this cabin 108 is discharged directly into the space 114 outside the fuselage through pressure reducing valve 110 in an amount corresponding to the difference obtained by subtracting the amount of leakage from the fuselage from the amount supplied by the air conditioner.
In conventional air conditioners, in order to control the temperature and pressure and to prevent the reduction of oxygen concentration such as to achieve comfort of the people in the cabin, it is necessary to increase the rate of air extraction from engine 101. It was therefore difficult to combine lowering of engine load with cabin comfort.
An object of the present invention is to provide an aircraft air conditioner capable of solving the above problems.
An aircraft air conditioner according to the present invention wherein air extracted from an engine that is fed through a main air flow path into an aircraft cabin is cooled by a cooling device comprises: an outflow air flow path for outflow of air in the cabin; an auxiliary air flow path for feeding air into the cabin; a plurality of adsorption sections respectively constituted of adsorption agent that adsorb molecules contained in the air and that release the adsorbed molecules by being raised in temperature to more than the temperature thereof on adsorption; an air flow path changeover mechanism; and a controller that controls the air flow path changeover mechanism, wherein each of the adsorption sections is made capable of being changed over between a condition in which it is connected to an auxiliary air flow path in which air of higher temperature than the air within the cabin flows and a condition in which it is connected to the outflow air flow path by means of the air flow path changeover mechanism; and each of the adsorption sections is changed over between the condition connected to the auxiliary air flow path and the condition connected to the outflow air flow path by controlling the air flow path changeover mechanism by the controller.
Preferably, the adsorption sections are constituted by at least either an adsorption agent capable of adsorbing water molecules or an adsorption agent capable of adsorbing oxygen molecules.
According to the present invention, when the air flowing out from the cabin into the outflow air flow path passes through the adsorption sections, the molecules contained in the air are adsorbed by the adsorption agent in the adsorption sections. When the air flowing in the auxiliary air flow path passes through the adsorption sections, since this air is of higher temperature than the air flowing out from the cabin, the molecules adsorbed by the adsorption agent in the adsorption sections are released into the air flowing in the auxiliary air flow path. Since the adsorption sections are changed over between a condition connected to the auxiliary air flow path and a condition connected to the outflow air flow path, the molecules contained in the air flowing out from the cabin can be returned into the cabin. Also, the adsorption agent in the adsorption sections is regenerated so that molecules in the air can again be adsorbed. If the adsorption agent adsorbs and releases water molecules, this adsorption and release of water molecules can contribute to maintaining humidity within the cabin. If the adsorption agent adsorbs and releases oxygen molecules, this adsorption and release of oxygen molecules can contribute to maintaining the oxygen concentration within the cabin. Furthermore, the present invention can easily be applied to small aircraft, because regeneration of the air in the cabin can be achieved by an uncomplicated construction of adding adsorption sections and a mechanism to change over the flow of air to these adsorption sections.
Preferably, when at least one adsorption section is connected to the auxiliary air flow path, at least one other adsorption section is connected to the outflow air flow path. In this way, adsorption and release of molecules into the air by the adsorption sections can be performed efficiently.
Preferably, there is provided a discharge mechanism capable of discharging at least some of the air flowing through the outflow air flow path to the space outside the fuselage in accordance with conditions during flight or the conditions of the air within the fuselage, after passing through the adsorption section. In this way, molecules contained in the air are absorbed before the air is discharged to the space outside the fuselage to maintain the pressure within the cabin at a suitable level, so molecules such as water or oxygen contained in this air can be effectively re-used. For example, it becomes even easier to maintain water vapor or oxygen concentration within the cabin at the target values, making it possible to greatly increase passengers"" sense of comfort. In particular, this is effective in preventing a lowering of humidity when there is little generation of water vapor within the cabin due to the number of passengers being small.
Furthermore, preferably a discharge changeover mechanism is provided whereby at least some of the air flowing through the outflow air flow path is changed over between a condition in which it is discharged into the space outside the fuselage via the discharge mechanism after passing through the adsorption section and a condition in which it is discharged to the space outside the fuselage via the discharge mechanism without passing through the adsorption section. In this way, when the need to re-use molecules contained in the fuselage air is high, the fuselage air is discharged to the space outside the fuselage after passing through the adsorption section and when the need to re-use this is low, the fuselage air is discharged into the space outside the fuselage without passing through the adsorption section. For example, when flying at high altitude, the fuselage air is discharged to the space outside the fuselage after passing through the adsorption section, but when on the ground at high temperature and high humidity, the fuselage air is discharged to the space outside the fuselage without passing through the adsorption section. In this way, cabin humidity can be maintained in a comfortable range when on the ground etc., since not only moisture adsorbed by the adsorption agent from the recirculation air flows is discharged but moisture can be contained in the air discharged to the space outside the fuselage.
Preferably the adsorption sections are constituted of an adsorption agent capable of adsorbing at least oxygen molecules, and air of oxygen concentration lowered in the adsorption sections is fed to a fuel peripheral region. In this way, occurrence of fuel fires can be prevented by nitrogen-enriched gas of lowered oxygen concentration.
Preferably it is arranged that the flow rate of air flowing through the auxiliary air flow path is adjustable. In this way, the temperature within the cabin can be suitably maintained by adjusting the ratio of the flow rate of air fed into the cabin after cooling by the cooling device to the flow rate of air fed into the cabin without cooling.
Preferably, a selectively permeable membrane is provided at a position through which air flowing in an air flow path of the air conditioner passes, so that it separates the air into nitrogen-enriched gas and oxygen-concentrated gas, wherein the nitrogen enriched gas can be fed into a fuel peripheral region and the oxygen-concentrated air can be fed into the cabin. In this way, occurrence of fuel fires can be prevented and the oxygen concentration within the cabin can be maintained.
Preferably the adsorption agent is made capable of adsorbing at least water molecules, and the selectively permeable membrane is provided in an air flow path in which air flowing out from the cabin through the outflow air flow path flows after passing through the adsorption sections. In this way, the air flowing out from the cabin can again be fed into the cabin as oxygen-concentrated air, and the necessary air flow rate for controlling the pressure within the cabin can be ensured without increasing the rate of extraction of air from the engine. Furthermore, since moisture is removed from the air fed to the selectively permeable membrane in the adsorption sections, the moisture released to outside the fuselage after passing through the selectively permeable membranes is reduced and the humidity in the cabin can therefore be maintained. Also, moisture can be prevented from becoming mixed with the fuel.
Preferably the adsorption agent is made capable of adsorbing at least water molecules, and arrangement is made such that the air flowing out from the cabin through the outflow air flow path can be fed into the cabin after passing through the adsorption sections and being adjusted in temperature suitable for the cabin. In this way, air flowing out from the cabin can be fed back into the cabin at a suitable temperature, and the air flow rate necessary for controlling the pressure and temperature within the cabin can be ensured without increasing the rate of air extraction from the engine. Furthermore, the humidity within the cabin can be maintained by returning moisture adsorbed in the adsorption sections into the cabin.
Preferably the air flow path is made capable of being changed over between a condition in which the air flowing through the auxiliary air flow path is discharged outside the fuselage and a condition in which it is fed into the cabin, after passing through the adsorption sections, and/or the air flow path is made capable of being changed over between a condition in which the air flowing out from the cabin through the outflow air flow path is fed into the cabin and a condition in which it is fed into the cooling device, after passing through the adsorption sections. In this way, when the temperature, humidity, oxygen concentration or pressure of the external air and/or the flow rate of the extracted air from the engine change in accordance with the condition of flight of the aircraft, the temperature, humidity, oxygen concentration and pressure within the cabin can be optimally maintained. Also, if the humidity within the fuselage is excessive, air containing moisture released from the adsorption agent can be discharged into the space outside the fuselage. In addition, when air flowing out from the cabin is again fed into the cooling device, dew formation of the cooling device can be prevented.
Preferably the auxiliary air flow path is constituted by a bypass air flow path for feeding air extracted from the engine to the cabin without passing through the cooling device. In this way, the adsorption agent can be regenerated by releasing molecules from the adsorption agent, because high-temperature air extracted from the engine passes through the adsorption sections.
Preferably the auxiliary air flow path is constituted by a circulating air flow path for feeding air flowing out from the cabin again into the cabin, and means for heating air flowing through the circulating air flow path before passing through the adsorption agent is provided. In this way, increase in the engine load can be prevented without needing to consume air extracted from the engine for regenerating the adsorption agent. The air flowing in the circulating air flow path can be heated by the heat emitted from electrical equipment mounted in the aircraft.
Preferably the auxiliary air flow path is constituted by a circulating air flow path for feeding air flowing out from the cabin again into the cabin, the adsorption agent is made capable of adsorbing at least water molecules, compression means is provided for compressing air flowing out from the cabin through the outflow air flow path downstream of the adsorption section; a heat exchanger is provided downstream of the compression means, for performing heat exchange between the compressed air and the air flowing through the circulating air flow path; and the air flowing through the circulating air flow path is heated in the heat exchanger prior to passage through the adsorption agent. In this way, the temperature of the air flowing in the circulating air flow path can be raised by the heat generated by compressing the outflowing air, so there is no need to provide a further heat source and energy consumption can thereby be reduced. By cooling the compressed air by means of air flowing out from the cabin through the circulating air flow path, the air temperature after compression can be appreciably lowered. Therefore, even when recooling is necessary, the cooling device for this purpose can be made smaller.
Preferably, a selectively permeable membrane is provided for separating the outflowing air cooled in the heat exchanger after compression into nitrogen-enriched gas and oxygen-concentrated air; and arrangement is made such that the nitrogen-enriched gas can be fed into a fuel peripheral region of the aircraft and the oxygen-concentrated air can be fed into the cabin. In this way, the air flow that passes through the selectively permeable membrane can be ensured without consuming air extracted from the engine. Furthermore, as a result of removing the moisture prior to arrival of the air at the selectively permeable membrane, there is no possibility of moisture flowing out through the selectively permeable membrane, and so discharge of moisture from the cabin and admixture of moisture with the fuel can be prevented. Also, nitrogen-enriched gas can be obtained efficiently by compressing the air fed to the selectively permeable membrane.
If a large quantity of nitrogen-enriched gas is required, the air needed for regenerating the adsorption agent is increased since the amount of air whose moisture has been adsorbed by the adsorption agent is increased. In this case, since the compressed air is also increased prior to being fed to the selectively permeable membrane, the amount of heat used to heat the air flowing out from the cabin through the circulating air flow path can be increased. The high temperature air needed to regenerate the adsorption agent is thereby ensured by the heating of the air. That is, a system with a good balance of air flow rates can be obtained.
According to the present invention, an air conditioner can be provided wherein the temperature, humidity, oxygen concentration and pressure within the cabin can be properly maintained without increasing the engine load, with improving comfort, and which can contribute to preventing occurrence of fuel fires and whereby dew formation of the cooling device can be prevented and furthermore which is suited both to large aircraft and small aircraft.